Preparation of polyester amides with zinc acetylacetonate catalyst



United States Patent Oifice 3,153,011 Patented Oct. 13, 1964 3,153,011PREPARATION OF POLYESTER AMIDES WITH ZINC ACETYLACETONATE CATALYST JackG. Scruggs, Cary, N.C., assignor, by mesne' asslgnments, to MonsantoCompany, a corporation of Delaware No Drawing. Filed Dec. 13, 1961, Ser.No. 159,157

" 8 Claims. (Cl. 260-75) This invention is addressed to the generalsubject matter of polyesteramide preparations. More particularly, it isconcerned with an improved method for obtaining polyesteramides bypoly-condensing terephthalic acid diamide- N,N'-di-e-caproic acid or itsester derivatives with a glycol in the presence of a novel catalyst.

It is known that a superior polyesteramide can be prepared fromterephthalic acid diamide-N,N-di-e-caproic acid or its ester derivativesand ethylene glycol. However, previously known procedures for preparingthese polymers have not been economic and the polymers obtainedtherefrom have been greatly discolored. These shortcomings have been forthe most part due to the unavailability of efiicient catalysts for usein forming these polymers. Despite the fact that a reaction somewhatanalogous to polyesterification is involved, it has been found thatconventional catalysts, such as manganese formate, are not active inreactions for producing the aforesaid polymers although they are highlyeffective in forming polyesters from, for example terephthalic acid andethylene glycol. Catalysts, such as lead oxide, boron and others havebeen previously employed in forming the polyesteramides to which thisinvention is addressed, but they have not possessed the necessaryactivity for satisfactory results. That is, when employed, thepolymerization reaction, which is conducted at high temperatures, mustbe so prolonged in order to obtain the desired degree of polymerizationfor polymers having fiber-forming characteristics that the polymersbecome degraded and develop undesirable color.

Accordingly, it is an object of this invention to provide an improvedprocess for preparing polyesteramides from terephthalic aciddiamide-N,N'-di-e-caproic acid or the ester derivatives thereof and aglycol.

It is a further object of this invention to provide a novel catalyticagent for use in the afore-mentioned process.

It is a still further object to provide a process for preparingpolyesteramides of the just described class with an improved color and ahigher molecular weight.

Other objects will be apparent from the description and claims whichfollow.

In general, these objects are accomplished by conducting a condensation.reaction between terephthalic acid diamide-N,N-di-e-caproic acid ordialkylester derivatives thereof with a glycol containing 2 to 10 carbonatoms in the presence of a catalytic amount of zinc acetylacetonate.

The di alkyl ester derivatives referred to above are 1 di-esters formedfrom lower alcohols, such as methyl-,

. corresponding mixed esters.

ethyl-, propyl-, butyl-, and amyl-alcohol as well as the The glycolsemployed are i polymethylene glycols of the general formula HO (CH OHboth in the presence of the catalytic agent zinc acylacetonate. In thefirst stage, the acid is retracted with an amount of ethylene glycolwhich exceeds the stoichiometric quantity to form the di-glycol ester ofthe acid. This monomer is then poly-condensed in the second stagereaction to form the polymer. The amount of ethylene glycol employed inthis reaction is not critical beyond therequirement that at least morethan a stoichiometric quantity be present. Generally, however, highproportions of the glycol relative to the esters or acids are used. Forexample, up to 10 times as many moles of glycol as ester or acid may beemployed because the reaction takes place more readily in the presenceof an excess of glycol.

The conditions necessary for these reactions are Well known and will bereadily understood by those skilled in the art. Thus, during the firststage in which the diglycol ester is formed, the reaction is carried outat atmospheric pressure and at a temperature in the range of from aboutto 195 C. and preferably between and C. At the completion of the firststage, the excess glycol is distilled off prior to entering the secondstage of poly-condensation. Thereafter, in the second or polymerizationstage the reactive intermediate, e.g., the bis-2-hydroxethyl ester ofterephthalic acid diamide-N,N'-di-e-caproic acid is heated at a stillhigher temperature of from about 230 to 250 C. and under reducedpressure within the range of from 0.1 to 5 mm. of mercury to form thepolymer. The second, or polymerization step is continued, if afiber-forming polymer is desired, until the reaction product has thedesired degree of polymerization, which may be determined by viscositymeasurements. Normally, high molecular weight polymers in thefiber-forming range can be obtained in from about 30 minutes to one hourof polymerization reac-,

tion time.

When employing the dialkyl esters of terephthalic aciddiamide-N,N'-di-e-caproic acid as a starting material, the proceduralsteps are essentially the same as outlined above. In the first stage, anester-interchange reaction is conducted between ethylene glycol and thedialkyl ester, for example, the dimethyl ester of terephthalic aciddiamide-N,N'-di-e-caproic acid at normal pressures and a temperature ofbetween 175 to C. The di-glycol ester of terephthalic aciddiamide-N,N-di-e-caproic acid is formed during this reaction togetherwith methanol which is removed from the reaction zone. The second, orpoly-condensation stage, is conducted at reduced pressures of from 0.1to 5 mm. of mercury at a temperature in the range of from 230 to 250 C.Again high molecular weight polymers can be obtained in from about 30minutes to an hour.

As has been noted, the zinc acetylacetonate catalyst is present in boththe first and second reaction steps which have been described above. Theamount of catalyst present may be widely varied and is not critical. Allthat is needed is a catalytic amount. For example, good results can beobtained with a catalyst concentration varying between 0.001 to 2.0percent by weight based on the terephthalic aciddiamide-N,N'-di-e-caproic acid or the dialkyl ester derivatives thereof,with from about 0.1 to 0.5 percent being of preference.

Of course, as will be recognized by those skilled in the art, thereactive intermediate which is polymerized to obtain the polymer may beprepared separately from the polymer forming reaction and used at alater time. It may'also be prepared by other means than discussed above,for example, by reacting terephthalic acid diamide- N,N'-di-e-caproicacid with ethylene oxide. Usually, however, this intermediate isobtained in the manner described. Regardless of how the reactiveintermediate is obtained, the polymerization reaction to form thepolymer is greatly accelerated in the presence of the novel zincacetylacetonate catalyst of this invention, and the high molecularweight polymer obtained is substantially free from color.

To further illustrate the invention and the advantages thereof, thefollowing examples are given, it being understood that they are intendedto be illustrative only and not limitative. All given parts are byweight unless otherwise indicated. In each of the examples presented,specific viscosity measurements have been taken. These values aredirectly related to the degree of polymerization attained and thepolymer molecular weight. Specific viscosity values in the range of fromabout 0.3 to about 0.6 represent fiberand filament-forming polymers.

Specific viscosity, as employed herein, is represented by the formulasp= Rel. where N Time of flow of the polymer solution inseconds Time offlow of the solvent in seconds Example I This example illustrates theformation of a polymer from terephthalic acid diamide-N,N-di-s-caproicacid dimethyl ester by employing a representative catalyst of the priorpractice, i.e., lead oxide.

35 parts of the dimethyl ester of terephthalic aciddiamide-N,N'-di-e-caproic acid, 15 parts of ethylene glycol and 0.2parts of yellow lead oxide were heated with stirring and in a nitrogenatmosphere to a temperature of between 190 and 200 C. for a period ofabout 45 minutes at which time the trans-esterification was complete.The resulting bis(2-hydroxyethyl) ester of terephthalic aciddiamide-N,N'-di-e-caproic acid was then heated to a temperature ofbetween 230 and 240 C. at a reduced pressure of 0.2 mm. of mercury.These conditions were maintained for a period of four and one-halfhours. The polymer recovered had a specific viscosity of 0.49 and wasbadly discolored.

Example II This example illustrates the practice of this inventionwherein terephthalic acid diamide-N,N'-di-e-caproic acid dimethyl esterwas used as a starting material.

125 parts of the dimethyl ester of terephthalic acid diamide-N,N-die-caproic acid, 280 parts of ethylene glycol and 0.125 part of zincacetylacetonate were heated at a temperature of from 185 to 190 C. atatmospheric pressure for one hour. During this trans-esterificationreaction, methanol was continuously taken .off over-head. Thetemperature was then raised to 245 C. in order to distill off excessglycol. The resulting bis(2-hydroxyethyl) ester of terephthalic aciddiamide-N,N'-di-e-caproic acid was then condensed with stirring at 245C. and under a reduced pressure of 0.1 mm. of mercury. After permittingthis poly-condensation reaction to run for one hour, a polymer wasrecovered which had a specific viscosity of 0.80 and was substantiallywhite in appearance.

Example III This example illustrates the practice of this inventionwherein terephthalic acid diamide-N,N'-di-e-caproic acid per se was usedas a starting material.

100 parts of terephthalic acid diamide-N,N'-di-e-caproic acid, 223 partsof ethylene glycol and 0.20 part of zinc acetylacetonate were heated ata temperature of between 185 and 190 C. at atmospheric pressure withstirring for 60 minutesf The reaction temperature was then raised 4 to245 C. in order to distill off the excess glycol. The resultingbis(2-hydroxyethyl) ester of terephthalic acid diamide-N,N'-di-e-caproicacid was then heated to a temperature of from 240 to 245 C. at a reducedpressure of 0.2 mm. of mercury. After permitting the poly-condensationreaction to continue for approximately one hour, a polymer was recoveredwhich had a specific viscosity of 0.85 and was substantially White inappearance. Fibers were fabricated from the polymer by extruding asample of the same through a conventional spinnerette. The spinningconditions employed were a melt temperature of 230 C., spinnerettetemperature of 255 C. and an extrusion pressure of 215 p.s.i.g.

Example IV This example illustrates an embodiment of this inventionwherein the bis(Z-hydroxyethyl) ester of terephthalic aciddiamide-N,N'-di-e-caproic acid was used as a starting material. I

20 parts of a bis-(Z-hydroxyethyl) ester of terephthalic aciddiamide-N,N-di-e-caproic acid, and 0.03 part of zinc acetylacetonatewere charged to an autoclave. The temperature was raised to 240 C.,beginning stirring at about C. and continuing stirring throughout theprocess. A vacuum of 0.2 mm. of mercury was then applied and thereaction was allowed to continue for one hour at a temperature in therange of from 245 to 248 C. The polymer obtained was of high molecularweight and white in appearance. Fibers were spun from the polymer at theconditions described in Example III.

It is observed that in Example I above where a representative catalystof the prior art was employed in the polymer preparation, four andone-half hours reaction time under poly-condensation conditions wererequired to produce a polymer having a specific viscosity of 0.49. Onthe other hand, in Example II where the catalyst of this invention wasemployed, a polymer was recovered after only one hour of reaction timewith a specific viscosity value of 0.80 as determined under theidentical conditions. The same order of improvement in the rate ofreaction over the control, Example I, is shown in Examples III and IV.It will be observed further that in Example I the polymer produced wasbadly discolored while in Examples II, III and IV, the polymer obtainedwas substantially white in appearance.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention as described hereinabove and as defined in the appendedclaims.

1. A process for preparing polyesteramides which comprises conducting acondensation reaction of a polymethylene glycol containing 2 to 10carbon atoms with a compound selected from the group consisting ofterephthalic acid diamide-N,N'-di-e-caproic acid and the lower dialkylesters thereof in the amount of zinc acetylacetonate.

2. A process for producing polyesteramides which comprises conducting anester-interchange between ethylene glycol and the dimethyl ester ofterephthalic acid diamide-N,N-di-e-caproic acid to form thebis(2-hydroxyethyl) ester of terephthalic acid diamide-N,N-di-ecaproicacid and subsequently poly-condensing said bis- (Z-hydroxyethyl) esterof terephthalic acid diamide-N,N- di-e-caproic acid, both theester-interchange and polycondensation reactions being conducted in thepresence of from 0.001 to 2.0 weight percent of zinc acetylacetonatebased on the weight of said dimethyl ester of terephthalic aciddiamide-N,N'-di-e-caproic acid.

3. A process for preparing the bis(Z-hydroxyethyl) ester of terephthalicacid diamide-N,N'-di-e-caproic acid comprising reacting ethylene glycoland terephthalic acid diamide-N,N'-di-e-caproic acid together in thepresence of from about 0.001 to 2.0 weight percent of zincacetylpresence of a catalytic acetonate based on the weight of saidterephthalic acid diamide-N,N'-di-e-caproic acid reactant.

4. A process for preparing the bis(2-hydroxyethyl) ester of terephthalicacid diamide-N,N'-di-e-capr0icacid comprising reacting ethylene glycoland the dimethyl ester of terephthalic acid diamide-N,N'-di-e-caproicacid together in the presence of from about 0.001 to 2.0 weight percentof zinc acetylacetonate based on the weight of said dimethyl ester ofterephthalic acid diamide-N,N-di-ecaproic acid.

5. A process for producing polyesteramides which comprises polymerizingthe bis(2-hydroxyethyl) ester of terephthalic aciddiamide-N,N'-di-e-caproic acid in the presence of a catalytic amount ofzinc acetylacetonate.

6. A process for preparing polyesteramides which comprises the followingsteps in sequence: (1) causing a compound selected from the groupconsisting of terephthalic acid diamide-N,N'-di-e-caproic acid and thedimethyl ester thereof to react with a quantity of ethylene glycol inexcess of the stoichiometric amount at a temperature in the range offrom 175 to 195 C., (2) thereafter continuing the reaction underpoly-condensation conditions of a reduced pressure in the range of from0.1 to 5 mm. of mercury and a temperature of from 230 to 250 C., withsteps (1) and (2) being conducted in the presence of a catalytic amountof zinc acetylacetonate.

7. A process for preparing polyesteramides which comprises the followingsteps in sequence: (1) causing terephthalic aciddiamide-N,N'-di-e-caproic acid to react with a quantity of ethyleneglycol in excess of the stoichiometric amount at a temperature in therange of from to C., (2) thereafter continuing the reaction underpoly-condensation conditions of a reduced pressure in the range of from0.1 to 5 mm. of mercury and a tem perature of from 230 to 250 C., withsteps (1) and (2) being conducted in the presence of from 0.001 to 2.0weight percent of zinc aoetylacetonate based on the weight of saidterephthalic acid diamide-N,N'-di-e-caproic acid reactant.

8. A process for preparing polyesteramides which comprises the followingsteps in sequence: (1) causing the dimethyl ester of terephthalic aciddiamide-N,N'-die-caproic acid to react with a quantity of ethyleneglycol in excess of the stoichiometric amount at a temperature in therange of from 175 to 195 C., (2) thereafter continuing the reactionunder polycondensation conditions of a reduced pressure in the range offrom 0.1 to 5 mm. of mercury and a temperature of from 230 to 250 C.,with steps (1) and' (2) being conducted in the presence of from 0.001 to2.0 weight percent of zinc acetylacetonate based on the weight ofterephthalic acid diamide-N,N'- di-E-caproic a'cid reactant.

References Cited in the file of this patent UNITED STATES PATENTS2,719,835 Sublett Oct. 4, 1955 2,857,363 Easley Oct. 21, 1958 2,901,466Kibler et al Aug. 25, 1959 3,033,826 Kibler et a1. May 8, 1962 FOREIGNPATENTS 524,969 Belgium Dec. 31, 1953

1. A PROCESS FOR PREPARING POLYESTERAMIDES WHICH COMPRISES CONDUCTING ACONDENSATION REACTION OF A POLYMETHYLENE GLYCOL CONTAINING 2 TO 10CARBON ATOMS WITH A COMPOUND SELECTED FROM THE GROUP CONSISTING OFTEREPHTHALIC ACID DIAMIDE-N,N''-DI-E-CAPROIC ACID AND THE LOWER DIALKYLESTERS THEREOF IN THE PRESENCE OF A CATALYTIC AMOUNT OF ZINCACETYLACETONATE.